Allow --resume to accept an optional session ID

[dabeedj]

Problem

Currently there is no way to resume a specific chat session by its ID from the command line. --resume always picks the most recent session for the current working directory, and --resume-picker requires interactive selection. This makes it impossible to script or automate resuming a particular session.

Proposed solution

Make --resume accept an optional session ID argument:

kiro-cli chat --resume                     # current behavior, resumes most recent
kiro-cli chat --resume <SESSION_ID>        # resumes the specified session

This would allow resuming any session directly by its ID without interactive selection.